A plug-in coupling has a coupling plug and a coupling socket. The coupling plug has an inner and an outer pipe piece and a first attachment flange and is connected to the first cryogenic line. The coupling socket has an inner and an outer pipe piece and a second attachment flange and is connected to the second cryogenic line. A circular annular seal on the distal end of the coupling plug is of electrically insulating form. An insulating sleeve is arranged on the outer pipe piece of the coupling plug. An insulating disc is situated between the first and the second attachment flange when the coupling plug has been inserted into the coupling socket. The plug-in coupling realizes a galvanic is separation between the coupling plug and the coupling socket.